Novel anion exchange membranes based on polymerizable imidazolium salt for alkaline fuel cell applications

Abstract

A new polymerizable imidazolium salt monomer, 1-(4-vinylbenzyl)-3-methyl-imidazolium chloride ([VBMI]Cl), has been readily synthesized by reaction of 4-vinylbenzyl chloride with 1-methylimidazole. Novel anion exchange membranes (AEMs) based on the copolymers of [VBMI]Cl and styrene have been prepared and characterized. Excellent thermostability of the membranes is observed through the thermo-gravimetric analysis (TGA) curves. Water uptake and ion exchange capacity (IEC) of the OH⁻ form AEMs range from 26.1% to 61.9% and from 0.95 to 1.45 mmol g⁻¹, respectively. This type of AEM displays significant ionic conductivities over the order of 10⁻² S cm⁻¹ in deionized water at room temperature, and the membranes are stable in 10 mol L⁻¹NaOH solution at 60 °C for 120 h. For the H₂/air single fuel cell at 30 °C with this novel AEM, the peak power density of 33 mW cm⁻² is obtained at a current density of 59 mA cm⁻².